Automatic telephone system



Feb. 28, 1933. V v. s. THARP AUTOMATIC TELEPHONE SYSTEM Filed Sept. 2, 1930 T0 LOCAL SELECTOR @ixn v 1,778,204, granted Oct.

Patented Feb. 28, 1933' vreron S. THARP, or nmvrnonsr, ILLINOIS,

ASSOCIATED ELECTRIC LABORATORIES,

TION OF DELAWARE ASSIGNOB, 13x MESNE ASSIGNMENTS, .ro INC., on cnroaeo, ILLINOI A CORPORA;

AUTOMATIG TELEPHONE SYSTEM Application filed September 2,- '1930. Serial No. 479,151.

This invention relates to automatic telephone systems in general, but is more particularly concerned with automatic telephone systems in whichcalls of certain classes .are given preference over calls of other classes. The invention has forits object a provision of new and improved circuits and apparatus for supplying this preferred service.

In some telephone systems, operating conditions makeit desirable to give toll calls preference over local calls. This condition is met in automatic telephone systems by providing special local and toll switchingapparatus.

In ordinary automatic telephone systems equipped for preferred service, the first selectors and connectors are provided with relays by means ofwhich a toll operator may effect the release of the switches. A typical system of thistype is disclosed in the United States patent to Wicks N 0. 1,742,334, of J anuary 7, 1930. Arrangements of this type, while entirely satisfactoryin operation, are not readily applicable to existing non-preferred service systems due to the extensive changes required in the selectors and connectors.

, In the so-called inverted the first selectors are provided with specialrelease controlling relays." A system of this type is shown in United States Patent No. 14, 1 930, to J. Wicks. This arrangement,however, is adapted for use only in systems in which talking battery systems only is supplied from the first switch of the train and is, of course, not applicable to the ordinary automatic systems. 7 7,

It will be seen from the foregoing, that known arrangements for supplying preferred service require the employment of-special local switching apparatus. When such'arrangements are to be added to existing nonpreferred service systems,extensive modification of the more-or-less complicated trunk switches, that is, selectors andconnectors, is required which is both difficult and expensive. The present invention is particularly adapted for installation under such condi-- tions.

The employment of the novel lineswitch which comprises a part ofthe inven 'andoconnector C are Well-known tion, or the modification of existing line's switches -in accordance with the invention makes it unnecessary to alter the regular ex change switching apparatus in any way. The various features of theinvention will be described in detail in the following specification, reference being had to the accompanying single figure of drawing which shows, by means of the usual circuit diagrams, certain apparatus of. a telephone system embodyingthe principles'of theiinven: tion. T

Referring now to. the drawing, there is shown a toll cord CO, by means of which connections are extended over the trunk line to a toll selector TS shown in skeleton form. The toll selector TS hasaccess to toll conn turn has access to Subscribers lines of which the line terminating in substation T is shown. This subscribers line is provided with the lineswitch LS which has access to local first selectors in the exchange. A second subscribers line terminating in substa tion T1 and its associated lineswitch LS1, is also shown. This lineswitch has access to local selectors, such as S, and by way of connectorsuch as C, can extend connectionsto substation T. I Cordcircuit CC may be ofanysuitable type arranged for dialling over a loop and the so-called dry trunk supervision. Toll selector TS may be an ordinary Strowger type selector with the provision of a fourth wiper for extending the holding conductor. Connector TC is also an ordinary Strowger typeconnector modified, however, in accord ance with the invention out in more detailhereinafter. fSelector S Strowger typelswitches, and since they form no part of the invention, they have been shown only nectors, such asthe connector TQ'which as will be pointed in skeleton form. Lineswitch LS is similar the invention may be gained from a detail de scription of the operations involved in setting up various connections in the system embodying the invention. As an example, it will be assumed that the operator desires to extend a toll call to the subscriber at substation T. The calling plug P of the cord circuit' CC is inserted in the jack of an idle trunkline, such as the jack J, after which the operator will actuate the calling device CD in accordance with the number of the wanted line. Toll selector TS operates in response to the first digit and selects an idle trunk, for instance, the trunk comprising conductors 1518 terminating in connector TC. Line relay 19of the connector operates over a; loop circuit which may be traced from battery, upper winding of relay 19, conductor 15, upper wiper ofthe selector, trunk conductor 2,ring of the jack and plug, contacts 14 of key K, contacts 10' of the calling device CD, contacts 12, tip" of the plug and jack, trunk conductor 1, lower wiper of selector TS, conductor 18, lower winding of relay 19 to ground at contacts 88 and 51. Relay 1900mpletes a circuit for relay 20 extending from ground at contacts 35, winding of relay 20, conductor 17, control wiper of selector TS, trunk conductor 3, sleeve of the jack and plug, contacts 19, winding-of relay 5 to battery. Relay 20 operates over the above circuit, applies holding ground to release trunk conductor 16 at contacts 37 to maintain the selector TS operated, grounds the local holding circuit of contacts 39, prepares the ime pulsing circuit of contacts 40 and opens the circuit of the release magnet at contacts 41. It will be noted that ground has been disconnected from the lower winding of relay 19 of contacts 38, but that the relay still receives ground by way of contacts 51. a The operator now proceeds to dial the next digit of the called number, thereby interrupt ing the previously-described loop circuit JEor relay 19 at impulse contacts 10. Relay 19 responds accordingly, and with the first retraction of its armatures, a circuit is closed from ground, contacts 45, 36,40, off-normal contacts 33, winding of slow-to-release relay 22, winding of vertical magnet 29 to battery. Relay 22 operates in response to this first impulse, and will remain operated throughout the seriesof impulses. The vertical magnet responds to the impulse and raises the wipers of the switch one step. The, oil-normal springs operate on the first step of'the wipers and prepare a new impulsing circuit the usual way, so that the second and succeeding impulse of the series are transmitted over a circuit including ofi-normal contacts 32 and contacts 46. Shortly after the last impulse of the series, relay 22 releases and extends the impulsing circuit-by way of contacts 47 to rlay 2 6 and the rotary magnet.

Relay 19 responds as in the previous case to the next series of impulses, and with each retraction of its armatures a circuit is closed over the previously-traced impulse circuit and contacts 47 winding of relay 26', contacts 82, winding of rotarymagnetBO to battery. The rotary magnet operates accordingly and rotates the wipers of the switch around to the contacts of the called line. Relay. 26. operates in series" with the vertical magnet, and, due to its slow-releasing characteristics, remains operated throughout the series of impulses. Relay 26 prepares a testing circuit by closing contacts 68, closes an auxiliary circuit around contacts 64' at contacts 69 to prevent interference from the busy relay as the wipers pass over contacts of the busy line.

t may be assumed, that the Wanted line,

that is the line extending to substation T, is

idle atthis time. Shortly after the last im- I pulse of the series, relay 26 will restore, at which time a circuit is closed frombattery, winding of rotary magnet 93 of lineswitch LS, contacts 107, Winding of cut-0E relay 91 of the lineswitch, test conductor 88, test wiper of the connector, contacts 66, upper winding of relay 28, contacts 81, 63, and 39 to ground. Relay 28 operates in this circuit, completes a holding circuit for itself at contacts 79, connects direct ground to the test wiper at contacts80 to partially operate cut-off relay 91 of the lineswitch, opensits original energizing circuit of contacts 81, disconnects the rotary magnet at contacts 82, opens a further point in the release magnet circuit of contacts 83, connects a source of ring-back tone to the upper talking conductor at contacts 78, and at contacts 77 and 84 connects the line wipers through to the talking conductors. Cut-'ofi' relay 91 of the lineswitch operates partially as previously stated, itscomplete operation being prevented by the well-known interlocking arrangement with line relay 92. Contacts 99 and 104 are opened, thereby disconnecting ground and line relay 92 from the line to prevent interference with the incoming call. Ringing current is now applied to the line from the ringing-current generator, lower winding of ring-cut-ofi relay 23, contacts 48 and 7 7 upper wiper of the connector, conductor 86, through the bells of condenser at substation T, conductor 89, lower wiper of the connector, contacts 84 and 54 to ground. The called substation bell is rung intermittently until the subscriber answers or until the connection is released. When the subscribed panswers,a direct current bridge is closed across thecalled line, thereby permitting relay 23 to operate in a well-known manner. Relay 23 completes a locking circuit for itself at contacts 53, opens the ringing circuit of contacts 48 and 54', completes the talking circuit at contacts 50 and 54, respectively, disconnects the previously-referred-to ground from the lowerwinding of relay. 19 at contacts 51, and opens the ring-back tone circuit of relay which will restore.

circuit at contacts '49. Relay 2l which is bridged across the talking conductor of the connects ground to the lower winding of relay 19 at contacts 43 in place of the ground previously connected to this relay at contacts 51, and connects ground to the local holding circuitat contacts 44, at the same time opening the previously-described impulse circuit of contacts45.

Referring now to the operators cord circuit, relay 5 on operating in series with relay 20-of the connector, completes a circuit by way of contacts 8 and 7 for lamp L. "The lamplights to indicate the'progress of the call as will be clear when the subsequent operation is considered. During the dialling operation key K is actuated which connects up the calling device CD in place of relay 6. After the called subscribers number is dialled, the operator will restore key K'to normal, thereby reconnecting relay 6 across the trunk and in series with the two windings of relay 19 of the connector. Relay 6 operates and removes the short circuit from around relay 4 at contacts 9. Relay 4 operates and opens the short circuit around resistance R. The current flow through resistance R is such that lamp L is not lighted. This condition prevails until the called subscriber hangs up, at which time battery-feed relay 21 will restore and disconnect ground from'the lower winding of relay 19 which will also restore, together with relay 6 of the cord circuit. Re lay 6 will again short circuit relay 4'which in turn will short circuit resistance R, and lamp L will glow to indicate that the called subscriber hung up. Th'erelease of relay-'19 has no further eiiect at this time, since relay 20 remains locked up to ground at contacts 37, and. the release magnet circuit is opened at contacts 41. The operator, on noting the lighted condition of lamp L, will withdraw plug P from the jack, thereby opening the Re lay 20 removes ground from the local holding circuit and release trunk, whereon relays 23 and 28 restore-and a circuit is completed by way of contacts 45, 36, 41, and '83, off-normal contacts 34, winding of'release magnet 31,

, to battery. The release'magnet operates to restore the switch to normal in the usual way. Off-normal springs 34 open when the wipers restore to normal, and-open the circuit'of the release magnet and the switch is now in readiness to receive the next call.

iVhen a call is extended to a line busy in another'connection, a somewhat different sequence of operations takes place. The line from substation T, for example, may be busy in either an outgoing or an incoming call.

' If busy in an outgoing call,- cut-ofi relay 91 called connectors,

will be operatediullyandtheline conductors will beextended overthe line wipers to a selector; The selector, in, well-known manner, groundsthe release trunk to hold cut- 0E relay 91 operated, and also by way of con ductors 88 and 96, marks the line busy in the banks of the various connectors. When the line is busy in an incoming call,*a conne ctor, such as connector 0, will be engagingtheline and ground on thetest wiper of the connector will serve to mark the'line busy in the multiple connector banks. operator will proceed to set up the connection exactly as described for the preceding connection. 'It will be recalled that relay 26 on operating completed the test circuit at,

contacts 68. When the wipers of the toll connector come to rest on the contacts of the busy wanted line, ground onthe test contact will cause relay to operate. Relay 25 completes an additional ground circuit for the lower winding of relay 19 at contacts 62, opens a point in the circuit of the upper winding ofrelay 28 at contacts 63, opens the impulsin'g circuit at contacts 64, prepares a lockingcircuit for itselfat contacts 61, and closes a point in thecircui'tof relay 24 at contacts 65. Shortly after the last impulse of the series, relay 26will restore in the usual manner, open the original energizing circuit of relay 25 at contacts 68, andcomplete a locking circuit for the-relay at contacts 67 I Relay 26 will also complete from ground, contacts 75, 7 0 and 65. Relay 24 operates, completes. a temporary talking circuit at contacts 56- and 60,'cl'oses a circuit for relay 23 at; contacts 57, and extends the impulsing V circuit, previouslydescribed, through to relay 27 bywayof contacts 58. Relay 23 operates and disconnects its lower winding from the talking conductors of the switch and prepares the. talking circuit as in previous connections. Since relay24'is op erated,battery-feed relay 21 will be disconnected from the talking conductors, and these conductors will beextended through to the wipers without battery or ground connections. The operator may now listen in on the conversation taking place on the busy line, battery being fed depending on whetherthe line isengaged in an incoming or outgoing call. The operator may {determine in this manner whether the line is engaged ina local call-or a toll call, and if so, whether'the waiting call is more important than the call in progress, If the new-call is to be given pre-' cedence, the operator will inform. the sub scriber that an important toll call is waiting, 1

a circuit for relay-2.4

from either-thecalling or In either'case the switch by way of contacts 71 and the auxiliarywiper of the connector, completes a new locking circuit to relay'25 by way of contacts 72 and 52, opens the circuit of relay 24 at contacts 75, and completes a circuit for the lower winding of relay 28 at contacts 74. Relay 24 will release and reconnect battery-feed, relay 21 to the talkingconductors. of the switch; Relav 28 operates, connects the-wipers of the switch through to the battery-feed relay, and opens the circuit of the rotary magnet and its own upper winding. Relay 90operates, and at contacts97 and 98 opens the talking conductors of the lineswitch and also disconnects the local connector multiple from the line and toll connector multiple. In the case of an outgoing call, the switching apparatus will, of course, be released when the calling line is disconnected as set forth. Incoming calls, however, will not be released,but will merely be disconnected from the line, after which, of course, the calling subscriber is expected to release the connection in the usual way. It will be noted thatthe loca'lconnector multiple is marked busy under .athese conditions by ground onthe test wiper of the toll connector. Ihus any other. local subscriber calling the sub-station T will receive the usual busy inindication. The. release of the connection, above described,is substantially the same as that previously described. Relays 25 and 27, which areenergized in addition .to the normally-energized relays are released following the deenergizationof relay 20. ;.\Vhat is considered new and is desired to haveprotected by. Letters Patent is set forth in the appended claims. ,What is claimed is; p I Y 1.. In apreferred-service telephone system, a toll switchboard, a subscribers line, an automatic switch, means at the switchboard for transmitting series of digit impulses to directively operate said switch, means in the switch responsivesolely to said impulses for estabtalking connection with said line lishing a line is busy in either a local connecwhen the 'tion or a toll connection, and means including a relay: in said switch controlled from the switchboardfor releasing the first connection provided the same is a local connection.

2. In a preferred-service telephone system, a subscribers line, an automatic switch operated're'sponsive to series ofdigit impulses for extending Y a talking connection to said line when the line is busy in either a local connection or a toll connection, and means in said 3. In a telephone system, an automatic ex:

change, a toll switchboard, subscribers lines terminating :in the automatic exchange, switching apparatus for completing local connections between said lines, other switching apparatus for extending toll calls from said switchboard to said lines, and means whereby toll calls maybe extended to lines engaged in local connections to the exclusion of such connections, said means including a relay individual to the Wanted line. I

4. In a preferred-service telephone system, 7

a subscribers line engaged in a connection of one class, means for selecting, the engaged line to establish a connection of anotherclass, and a relayindividual to the linefor releasing the first connection.

v:5. In a'preferred-service telephone system, a subscribers line engaged in a connection of one class, an automatic switch for selecting the engaged line to establish a'connection of another class, a relay individual to the line for releasing the connection of said one class, and means in said switch for operating said relay.

, 6. In a preferred-service telephone system, a subscribers line which may be engaged in either anincoming or outgoing connection of asubsc-ribers line engaged in a'local connection, a toll switchboard, means for extending a talking connection from the switchboard to said engaged line, a relay individual to the line forreleasing said local connection, and

means controlled from the switchboard for operating said relay. 9. In a preferred-service telephone system, a subscribers line engaged in a local connection, atoll switchboard, automatic switches operated responsive to dialled impulses transmitted from the switchboard for extending a connection to said engaged line, and a relay individual to the line operated responsive to additional dialled impulses transmitted from the switchboard for releasing said local connection. 7

10., In a telephone system, contact banks bank, a toll connector bank, a subscribers line connected to a set of contacts in each of said banks, and a relay for disconnecting the line from the set of contacts in said local connector bank.

13. In a telephone system, a local connector bank, a toll connector bank, a subscribers line connected to a set of contacts in each of disconnecting the line from the set of contacts in said local connector bank, and a circuit for said relay including a contact in said toll connector bank.

14. In a telephone system, a line terminating in a set of contacts comprising two-line contacts and a test contact accessible to toll connectors, multiple connections between said set of contacts and a corresponding set of contacts'accessible to local connectors, and a relay for opening the multiple connections between the line contacts of said two sets.

15.. In a telephone system, a line accessible in two sets of bank contacts, one set comprisingtwo-line contacts and a testv contact and the other set comprising two-line contacts, a test contact, and an auxiliary contact, multiple connections between the line and test contacts of said two sets, a relay connected to said auxiliary contact, and contacts controlled by said relay for opening the multiple connections between the line contacts of said sets.

16. In an automatic telephone system of the type in which calls of one class are given precedence over calls of another class, subscribers lines terminating in two sets of multiple contact banks over which said two classes of calls are extended respectively, and relays for disconnecting the lines from one 1 of said sets of banks.

17. In a telephone system, a subscribers line normally connected to a line switch, a toll connector bank and a local connector bank, a relay for disconnecting the'line from adapted to operate responsive to two series of impulses to set its wipers on the contacts of a called line, means responsive when the called line is busy in another connection for additional series of impulses for interruptadapting the connector to respond to an additional series of'impulses, and a relay individual to the line operated responsive to said ing the first connection.

. 19. In a connector switch provided with a set of wipers comprising two test wiper and a control wiper, stepping magnets operated responsive to two series of digitimpulses for setting said wipers on the contacts ofa called line, a relay operated over said test wiper when an idle line is connected with for connecting said line wipers to the talking conductors of the switch, a second-relay adapted to operate responsive to an additional series of digit impulses when line wipers, a

' a busyline is connected with,and means controlled by said' second relay for completing an operating circuitfor said first relay and for connecting a characteristic potential to 7 said control wiper. said banks, a relay 1nd1 v1dual to the lln'eifor 20. In a preferred-service telephone sys-. tem, a subscribers line, an automatic switch, means for transmitting series of impulses to the switch to set the same, means in the switch responsive solely to said impulses for extending a talking connection to the line when the line'is busy in either a local connection or atoll connection, and means-in the I switch responsive to an additional series of impulses forreleasing the first connection provided the same is a local connection.

In witness whereof, I hereunto subscribe mynaine this 28th day of August, A. D. 1930.

' VICTOR S. THARP. 

